The spinner when importing your data source means that Xcalar Design is working to process your dataset preview or import. If using XD accessing large data source files from Azure Blob Storage, you will run into the spinner unexpectedly prior to a preview. During preview, usually XD parses a partial file to assess source data format, but Azure Blob only returns entire files. As a result, it will take a while to preview data source files from Azure Blob

The best practice is to split large data source files into smaller files. That way, XD won't need to parse your entire dataset to preview. In addition, splitting data source files will allow XD take full advantage of parallel processing of your multi-node cluster, when completing the import process.